[sdiy] Frozen DX7IID

[The Old Crow]

   This might be a bad address decoder. I think it was an 'HC138, I'll 
have to look. --Crow

On 8/21/2014 3:37 PM, greg at gzifcak.net wrote:
> Hello,
>
> I just replaced the RAM in my DX7II. I swapped the existing Toshiba
> TC5564PL-15 chips for TC5564APL-15 since this is all I could find
> available. I searched for info on the meaning of the suffix but couldn't
> find anything.
>
> Anyway, I did not try powering it on before I did the repair, but it
> worked fine (aside from the RAM) when I last used it about a month ago or
> so.
>
> When I powered it on after replacing the RAM chips, all lights came on and
> the screen is blank except for the top row, which is showing solid bars.
> It is making no sound and no panel controls have any effect.
>
> I probed around with my scope and the sub-CPU and main CPU are both
> receiving clock and show approximately 5v on the power pins.
>
> Any ideas what else to check or should I hunt for replacement CPUs?
>
> Thanks in advance,
> Greg
>
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